Classification of Epilepsies and Epileptic Syndromes
What we call epilepsy is not just one disorder. The epilepsies are a diverse group of disorders, with some shared features and some that are distinctly different. A classification system provides us with a logical, organized approach and gives us a universal language shared among health professionals all over the world.
Two systems of classification of epilepsies are in use today. The International League Against Epilepsy (ILAE) Classification of Epileptic Seizures 1981 divides seizures into three types, with subtypes of each:
- Partial (seizures involving only part of the brain)
- Generalized (seizures involving both sides of the brain)
- Unclassifiable
The advantage of this system is that seizures can be classified relatively easily and the choice of medication is dictated by seizure type.
A problem presented by this simple classification system is that the same patient may have more than one type of seizure, either together or in sequence. Many patients' seizures also change over the course of their illness. These problems paved the way for another system of classification-the ILAE Classification of Epilepsies and Epileptic Syndromes 1989. This system is meant to supplement the previous classification, not to replace it. An epileptic syndrome is defined as a disorder characterized by a cluster of signs and symptoms occurring together. According to this system, epilepsies are divided into four broad groups:
- Localization-related (involves one or more distinct parts of the brain)
- Generalized (involves both sides of the brain at the same time)
- Undetermined whether localized or generalized
- Special syndromes.
Within the localized and generalized groups, there are further subdivisions into idiopathic (unknown cause), symptomatic (identifiable cause), or cryptogenic (hidden cause). This classification system is complex and many syndromes are not adequately defined. Look elsewhere on this website for more information on many of the syndromes listed.
When seizures first begin, it may not be possible to identify the syndrome. Not all patients fit into a specific syndrome and some need to be classified into nonspecific categories. With the continued advances in modern medicine, however, the classification of the epilepsies will continue to evolve.